1. Field of the Invention
The present invention relates to a sample observation method and a microscope used for observing a sample such as an electronic device, and a solid immersion lens used in the method and optical contact liquid for the solid immersion lens.
2. Related Background of the Invention
An electronic device as a sample is observed by a microscope or the like during inspection of the electronic device such as a semiconductor device, and a method for performing failure analysis and reliability evaluation of the electronic device is used. An emission microscope and an IR-OBIRCH apparatus or the like are conventionally known as an apparatus for inspecting a semiconductor (see Document 1: Japanese Patent Application Laid-Open No. H07-190946, and Document 2: Japanese Patent Application Laid-Open No. H06-300824). However, electronic devices which are inspection objects have been miniaturized in recent years, and the fine structure is difficult to analyze by a limitation caused by the diffraction limit of an optical system in a conventional inspection apparatus using visible light and infrared light.
Therefore, when the above fine structure of the electronic device is analyzed and the positions of an abnormality generated in the circuit patterns of transistors and wirings or the like formed in the electronic device are detected, the range where the abnormal positions exist is first narrowed down to some extent by an inspection apparatus using visible light, infrared light or heat rays. A method for inspecting the abnormal positions of the electronic device is used, in which the range narrowed down is observed by using an observation device such as an electronic microscope having high-resolution.
As described above, in the method for observing in high-resolution using the electronic microscope after inspection using light is performed, a problem exists in that much labor and time are required for inspecting the electronic device since the preparation and setting of the electronic device which is an inspection object are complex.
On the other hand, a solid immersion lens (SIL) is known as a lens for magnifying the image as the observation object. The solid immersion lens is a hemispherical lens or a hyperhemispherical lens which is called Weierstrass sphere. When the solid immersion lens is set so as to be brought into optically-close contact with the surface as the observation object, numerical aperture NA and magnification can be increased, and observation at higher spatial resolution is enabled. For instance, examples of electronic device inspection apparatuses using the above solid immersion lens are disclosed in Document 3: Japanese Patent Publication No. H7-18806, and Document 4: U.S. Pat. No. 6,594,086.